The present application is directed towards raiser seats for assisting a person from a sitting to a standing position. It is particularly applied to raiser seats in which the motion of the seat is determined by cams.
A variety of seats which can be raised or lowered in order to assist people from a sitting to a standing position are known. These are applied in many fields, and are of particular use in recovery from operations or for people with limited abilities. These seats may be a simple chair, or may also be used in medical transfer chairs, commodes or wheelchairs.
An example of a raiser seat is discussed U.S. Pat. No. 5,513,867 (Bloswick et al). This patent relates to a seat-lift wheelchair. The seat can pivot about its front edge to assist a person in standing up. The lift of the seat is achieved by the action of a tension spring pulling on a cable. The cable acts around a cam attached to the bottom of the seat. This cam determines the effective distance of the tension in the cable from the pivot point in the seat. It therefore allows the torque to be varied depending on the position of the seat.
This mechanism requires a large tension spring in order to generate the required torque. It will also only function correctly when the pivot point of the seat is fixed relative to the seat frame and the tension spring.